This kind of problem is best tackled using recursion. It's difficult to
write your first recursive stylesheet, but it's a very powerful technique to
have under your belt.
Basically you need to write a template that processes one of the siblings,
passing it the value of your "counter" or "running-total" as a parameter.
The template needs to make whatever changes are necessary to the counter or
running total, then make a recursive call to process the next element if
there is one, passing the new value of the counter or running total as a
parameter. When the final sibling is reached, you return (or write to the
output) the final value of the counter.
You can do this either with call-template or apply-templates (perhaps using
a special mode). I find it easier to use apply-templates, for two reasons:
(a) the current node is passed as an implicit parameter, and (b) the
recursion often terminates naturally when there are no more siblings.
Here's an example that totals @price*(_at_)qty over a set of sibling elements:
<xsl:template match="order">
<total-value>
<xsl:apply-template select="order-item[1]">
<xsl:with-param name="running-total" select="0"/>
</xsl:apply-templates>
</total-value>
</xsl:template>
<xsl:template match="order-item">
<xsl:param name="running-total"/>
<xsl:choose>
<xsl:when test="following-sibling::order-item">
<xsl:apply-template select="following-sibling::order-item[1]">
<xsl:with-param name="running-total" select="$running-total +
(@price*(_at_)qty)"/>
</xsl:apply-templates>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$running-total + (@price*(_at_)qty)"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
I hope you can see how to adapt this technique to your problem.
Michael Kay
http://www.saxonica.com/
-----Original Message-----
From: Agnisys Technology (P) Ltd. [mailto:agnisys(_at_)yahoo(_dot_)com]
Sent: 09 September 2005 21:31
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: Re: [xsl] Traversing the tree
David,
My real problem is a little more complex as it turns out,
and I'm stuck again!
What if instead of using the count or sum functions, I need
to use my own function for each of
the nodes after the one with an "offset"? Can I still use
some creative Xpath operation?
For example:
Input:
<top>
<a>
<reg > A1 </reg>
<reg offset="5" > A2 </reg>
<reg > A3 </reg>
<section>
section_foo
</section>
<section>
section_bar
</section>
<reg > A4 </reg>
</a>
</top>
Assume there is a "sizeNode" function that returns a "size"
of "section".
sizeNode(section_foo) = 10
sizeNode(section_bar) = 100
So, the output of the above should be :
A1 : 0
A2 : 5
A3 : 6
section_foo : 7
section_bar : 17
A4 : 117
So now I cannot use the following because the "size" of each
"section" could be different.
sum($x/@offset) +
(count(preceding-sibling::reg|preceding-sibling::section) -
count($x/preceding-sibling::reg|preceding-sibling::section))
I need some way to add up "size"s of all the nodes after (and
including) the node with an "offset"
attribute.
Once again I'm tempted to use a for loop and have a running
counter, but I'm sure there is a
better way.
I would appreciate any help/pointer in this regard.
Anupam.
P.S: Jay thanks for your effort, for me it was more food for thought.
--- "Agnisys Technology (P) Ltd." <agnisys(_at_)yahoo(_dot_)com> wrote:
David,
Your alternate strategy works well and solves the problem.
Although, I do need to study it carefully to understand
how it is doing it!
Thanks,
Anupam.
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